Rotationally Commensurate Growth of MoS2 on Epitaxial Graphene

TL;DR

This paper demonstrates the wafer-scale, van der Waals epitaxial growth of MoS2 on epitaxial graphene, resulting in a nearly strain-free heterostructure with registry and tunable electronic properties, advancing 2D material integration.

Contribution

It introduces a chemical vapor deposition method for direct, transfer-free growth of MoS2 on epitaxial graphene with controlled orientation and minimal strain, enabling high-quality heterostructures.

Findings

Nearly strain-free MoS2 achieved on graphene

Registry between MoS2 and graphene confirmed by X-ray and STM

Reduced bandgap of ~0.4 eV at MoS2 edges

Abstract

Atomically thin MoS2/graphene heterostructures are promising candidates for nanoelectronic and optoelectronic technologies. Among different graphene substrates, epitaxial graphene (EG) on SiC provides several potential advantages for such heterostructures including high electronic quality, tunable substrate coupling, wafer-scale processability, and crystalline ordering that can template commensurate growth. Exploiting these attributes, we demonstrate here the thickness-controlled van der Waals epitaxial growth of MoS2 on EG via chemical vapor deposition, giving rise to transfer-free synthesis of a two-dimensional heterostructure with registry between its constituent materials. The rotational commensurability observed between the MoS2 and EG is driven by the energetically favorable alignment of their respective lattices and results in nearly strain-free MoS2, as evidenced by synchrotron X-ray scattering and atomic-resolution scanning tunneling microscopy (STM). The electronic nature of the MoS2/EG heterostructure is elucidated with STM and scanning tunneling spectroscopy, which reveals bias-dependent apparent thickness, band bending, and a reduced bandgap of ~0.4 eV at the monolayer MoS2 edges.